Reversible-circulation internal fan kiln



R. THELEN REVERSIBLE CIRCULATION INTERNAL FAN KILN Filed NOV, '7, 1923 S-Sheets-Sheet l o ooooooooooo /O/ lad-L oooooooo ooooo oo oo oo .vo/WM oo o uoooo oo E oo oo oo oo oo ook\ June 23, 1925.

INVENTOR. v @Lr-1 IHELEN 115km, BY 0L W m v ATTORNEY June 23, 1925.

R. THELEN REVERSIBLE CIRCULATION INTERNAL FAN KILN 3 Sheets-Sheet 2 IN VEN TOR.

Filed Nov, '7, 1923 ATTORNEY June 23, 1925.

R. THELEN REVERSIBLE CIRCULATION INTERNAL FAN KILN Filed Nov. 7, 1923 3 Sheets-Sheet 5 Kwx.,

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vUNITED STATES 1,543,459 PATENT OFFICE.

ROLF THELEN, OF MADISON, WISCONSIN, DEDICATED, BY MESNE ASSIGNMENTS, T0 THE CITIZENS OF THE UNITED "STATES AMERICA.

REvERsIBLE-omcULATIoN INTERNAL EAN KILN.

Application filed November 7, '1923. Serial No. 673,340.

(GRANTED UNDER' THE ACT 0F MARGH 3, 1883; 22 STAT. L. 625.)

To all 'whom t may concern:

Be it known that I, ROLF THELEN, a citizen of the United States of A merica, `and an employee of the Department of Agriculture, residing in Madison, Wisconsin (whose post-office address is Madison, Wisconsin), have invented a new and Improved Re-I versible-Circulation Internal Fan Kiln.

This application is made under the act of March 3, 1883, Chapter '143 (22 Stat. 625), and the invention herein' described and claimed may be used by the Government of the United States, its officers and employees, and by any person in the United States without the payment to me of any royalty thereon. I hereby dedicate the same to the free use of the Government and the people of the United States.

My invention consists in an improvement in the design of forced circulation kilns or chambers for drying and conditioning lumber or similar material. However, its use is not limited to wood or wood products. It consists in the adaptation offans of the disk type, or similantypes, to the production of a unique internal circulation of air and the vapor in the kiln combined with the production and regulation of the heat and the humiditywithin the kiln.

This invention is illustrated in Figures 1 to 4. Figure 1 represents a cross-sectional elevation of an end piled kilntaken on the line l-l of Fig. 2 looking inthe direction of the arrows. Figure 2 represents a horizontal cross-section. Figure 3 is a vertical longitudinal section showing some of the fan details. Figure 4 is a cross-sectional elevation of a cross piled kiln. s

The principal feature which I claim as novel and an improvement lover existing kilns is the use and arrangement of the'fans and the air distributing system. This arrangement is such that a very fast and uniform circulation of air and vapor through the piles of lumber maybe secured and it permits the periodic reversal of the direction of the air movement by simply reversing the direction of rotation of the fans. The air distributingsystem provides a very uniform flow of y air ,throughout the length and breadth of the kiln and eliminates the non-uniformity of drying, which is one of the commonest troubles Iexperienced in the ordinary kiln. The arrangement of the4 fans upon a single shaft extending throughout the length of the kiln provides a simple means of producing brisk circulation; and the elimination of comparatively small ducts such as those used in external blower kilns reduces very materially the work required, to produce a given circulation. The differences in air pressure required in the operation of this kiln are much smaller than those ordinarily required in kilns employing centrifugal blowers, and the disk fans operate very' efficiently at these low pressures. Measurements recently made in dicate that the static pressures necessary for the successful operation of this system are materially less than one-eighth of an inch of water pressure. It ispossible, therefore, by the use of this invention to produce a very great and uniform circulation of air and vapor within the kiln with a very small eX- penditure of power.

While it is ob'vious that there are many possible ways in which the use of internalv I fans can be adapted to dry kilns of different types, this invention isy limited to single track kilns in which the lumber is edge stacked. 1n edge stacked lumber the width of each board is ina vertical direction, the thickness and length ,being in horizontal directions.

Any well-known means of heating the air and the vapor in the kiln may -be usedin conjunction with this invention. When steam pipes are used they may be arranged .beneath the lumber piles at the sides of the able means for accomplishing the same pur.-

. the invention limited to the specific rform of.

rails, trucks, andtrack supports illustrated in the drawings and described inthe speciication. l

Referringto Figures l, 2, 3, and 4, which are correspondingly lettered: AA represent the side'deflecting partitions. 'lhese partitions serve to form a passageway for the air from the spaces at the sides of the kiln to the fans and vice versa, the air moving in a more or less horizontal direction either inward towards the fans or outward from them, depending upon thedirection of the rotation of the fans. BB are the fans producing the circulation. Straight-bladed disk fans are preferable. Anytype of fan, how- Y ever, in which the reversal of the direction 'of rotation of the fan produces a reversal in the direction of the How of the air ourh rent passing through the fan can be used.

- CC are the shafts upon which the fans are or collars and `equi ping all of the other bearings, Il, on eac shaft with any wellknown meansr for x longitudinalr motion.

Plain bearings androller bearings require n o special provision of this kind. Certain types of ball-bearings require housings which permit the entire bearing to slide 1ongitudinally withinthem. DD are air inlet ampers used. to re "late and control the 'amount of air entering the kiln from. the

outside. EE are the heating coils. These may lbe ofthe return bend type o r other convenient type. FF are the steam jet pipes used lto increase the humidity of the air 1n the kiln. Suitable opening'sare provided tb permit the escape o the steam throughout ther lengthof the kiln.. '.{Yarious other common and wellsknown arrangements vmay be used. GG are the.lumber,-supportinl trucks. HH are the shaft hangersipll are earings` for the shafts CC. JJ'are the tracks upon.

which the lumbersupporting trucks. run.

KK are 4the Isiclewwalls,of the kiln. LL is i the lumber to bei dried. MM ,are'the track supports. N is-theshaft pulley. OO are air :outlet dam' ers for v controlling .the amount of airv ing exhausted from the kiln. P is a belt passing over the 1pulle s N and Q. Q-is'the, motor pulley. is t e l -motorwhich furnishes tlepower to drive lthe fans.l S isjafswitch for controll' g the .speed and rotation of the notor ar ature. I

While the drawings show and the specification describes' an electric motor, any other suitable driving meansA may be used. TT are air 'inlet lues in which the dampers DD \are tted. UU are the airv outlet lues in which the dampers OO are fitted.` WW are they side air passages between the piles of lumber and the side walls of the kiln. XX is the main air dis-` tributor. YY are the'upper diifusers. ZZ are the lower diffuscrs. The plenum chambers between the upper difl'users and the lower diflusers are the secondary plenum chambers. bb are the fan housings and partitions. ce are the plenum chamber partitions. v

The operation of vthe kiln is briefly as follows: The lumber is placed in the kiln, the doors and all of the dampers are closed, and the kiln is started. Steam is turned into the coils and the steam jets are turned on. Suitable regulating devices are provided to control and regulate the supply of steam to the heating coils and the supply of steam to the steam jets. lf it is found impossible to reduce the humidity to the desired point with the steam jets all turned ofi", the dampers DD and O O are opened to allow fresh air to enterv and moist air to escape. These dampers should be adjusted so that a humidity below that desired will be secured. The steam jets may then supplyra suftic'ientlamount of steam to 'bring the humidity up to the desired point.v If the direction of rotation of the motor, the shafts, andthe fansv is such that the 'air and vapor pass upward through'the lumber piles LL, said air and vapor will pass downward through the side air passages WW, over the heating coils EE, past the side delecting partitions AA, through the fans BB, into the-main air distributor X, which acts as a plenum chamber, a slight pressure being 'maintained through the action of the fans and the resistance of the upper and lower difl'users..y The air and vapor then pass yfrom the'main air distributors .through the flower diusers ZZ. The resistance of the upper diffusers YY serves to maintain a .115'

s11 ht plenum betweenthe upper and lower di users. TheI air. and vapor then pass upv'ward through the upper d iii'users and into the -piles of lumber, repeating the cycle continuously. When the direction of rotation of the fans is reversed, the direction of the circulation of the air and vapor is likewise reversed. The use -of the two sets of diffusers. in the manner indicated produces a very uniform flow of air through `the length ofthe kiln. The unbalancing effect of the horizontal air flow produced by the fans. is

practically eliminated by allowing a slight pressure, to buildup in the mainv air distributor. This is still further eliminatedby the slight plenum in the space betweenithe loss in efficiency which they cause. It is also obvlous that any well-known form of distr1buto'r may be used. The invention is not restricted to the form illustrated in which the openings consist simply of spaces between the slats running the full length of the kiln. l

When the direction of air circulation is downward through the lumber piles, the air distributing system, which consists of the main air distributor, thesde deflecting partitions, the plenum hambers, and the upper and lower diffusers, does not materially assist in producing a uniform air circulation. The'compare .v travel from the fans to the point at which the air enters the lumber has been found suflicient to produce the desired uniformity. The arrangement of the heating coils shown in Figure 1 also materially assists in smoothing out unevennesses in the circulation when it is upward in the side passages VVV. It

has been found through experience ewith av great many diilerent types of forced circulation in dry kilns that it is not possible to secure uniformity of air distribution if the air be handled at high velocities. In orderto produce uniform satisfactory circulation it is essential that thel air be moved at low velocities and that special means be provided for the uniform distribution of the air throughout the 'ki-ln. The use of internal fans and large plenum chambers produces this result since the velocity of the air through the fans themselves is comparatively low and the velocity within the plenum chambers is so small that the velocity head cannot be measured with manometers and similar instruments usually used for the purpose.

It is well understood that when the circulation of air and the vapor in the kiln is continuously in one direction, that portion 'of the pile at which the air 'enters will dry more rapidly than .the opposite side since the air in its passage through the lumber picks up moisture and thus reduces'its drying capacity. The reversal of the direction of the air circulation overcomes this defect since that edge of each lumber pile which was the entering air edge before reversal becomes the leaving air edge after reversal. Those portions of the piles which d ried fastest before reversal dry most sl'owhv 'v I,"feat-length of airl after reversal. The reversal of the circulation will in practice be done periodically every two or three days or oftener, the exact period being determined by the condition of the lumber in the kiln.

Several arrangement of the plenum cham-t bers are possible and practicable. The principal object of the plenum chambers and ditl'users is to produce a uniform flow of air and vapor through the lumber to be dried, and any detailed arrangement which will accomplish this result will be satisfactory if at the same time it does not consume an excessive amount of power. Experience has shown that it is in general desirable to have each fan. work independently of the other fans. This proudces greater uniformity of air distribution in that it prevents the accumulative etl'ect of any slight irregularities which might exist in the air distribution from each fan. "hen the direction of the circulation is reversed a similar tendency exists unless the side detleeting partitions A are especially designed to avoid this. The present invention contemplates the use of plenum chamber partitions and side deflecting partitions of the proper form and number to avoid such longitudinal air n'lovemei'it.

Having fully described the principles of this invention and the manner in which they 7 can be embodied in a dry kiln, I claim as origln al 1 l. In a single track dry kiln arranged for edge stacking: a series of fansta shaft on which the fans are. mounted for rotation; means for rotating said shaft in either direction to cause reversal of the circulation of the air and vapor in said kiln; and an air distributing systeln comprising side detleeting portions, a main air distributor, and two sets of dilusers. v

2. In a single track dry kiln arranged for edge stacking: a` series of fans; a shaft on which the fans are mounted for rotation; means for rotating said shaft in either direction to cause reversal of the circulation of the air and vapor in said kiln; damperedl air inlet lues and dampered air outlet lues; means for heating the kiln and its content-s; and an air distributing system comprising side deiecting partitions, a main air distributor, and two setsof ditfusers.

3. In a single track dry kiln arranged for edge stacking: a series of fans, a shaft on which the fans are mounted for rotation; means for rotating said shaft in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inletflues and dampered air outlet flues; means for heating the kiln and its contents; means for humidifying the atmosphere in the kiln; and an air distributing system comprising side detiecting partitions, a main air distributor, and two sets of ditfusers.

4. In a single track dryv kiln arranged for lill lill) the air and vapor in said kiln; damperedt air inlet flues and dampered air outlet fines; means for heating the kiln and its contents; a plenum chamber for each fan; and a diftuser with restricted discharge passages for each plenum chamber.

6. In a single track dry kiln arranged for edge stacking: a series of fans; a shaft on which the fansare mounted for rotation; means for rotating said shaft in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered a-ir inlet flues and dampered air. outlet fines;

means for heating the kiln and its contents;

means for humidifying the atmosphere in the kiln; a plenum chamber for each fan; and a diffuser with restricted discharge' passages for each plenum chamber.

In a single track dry kiln arranged for edge stacking: a series of fans; a shaft on which the fans. are mounted for rotation; means for rotating said shaft in either direction to cause reversal of the circulation of the air and vapor in said kiln;-a series of plenum chambers for each tan; and a diEuser with restricted discharge passages for each plenum chamber.

8. In a single track dry kiln arrange-d for edge stacking: a series of fans; a shaft on the air and vapor in said kiln; dampered air inlet fines and dampered air outlet lines;

means for heating the kiln and its contents; A

' a series of plenum chambers for each fan;

and a diffuser with restricted discharge passages for each plenum chamber.

9. In a single track dry kiln arranged for edge stacking: a series of fans; a shaft on Which the fans are mounted for rotation; means'for rotating said shaft in either direction to cause reversal of the circulation of the air and vapor 'in said kiln; dampered air inlet tlues and dampered air outlet flues; means for heatin the kiln and its contents; means for humi ifying the atmosphere in the kiln; a series of plenum chambers for each fan; and a diEuser with restricted discharge passages for each plenum chamber.

10. In a single track dry kiln arranged for edge stacking: a series of internal fans; a plenum chamber for each fan; and a diuser with restricted discharge passages for each plenum chamber.

Y11. In a single track dry kiln arranged for edge stacking: a series of internal fans; a series of plenum chambers for each fan; vand a diffuser with restricted discharge passages for each plenum chamber.

' February 10, 1925.

ROLF THELEN. 

